Aluminum alloy as bearing metal



Patented Apr. 9, 1940- PATENT OFFICE- 2,196,236 ALUMINUM ALLOY As BEARING METAL Eugen Vaders, Frankfort-on-the-Main, Germany, asslgnor to Verelnigte Deutsche Metallwerke Aktiengesellschaft, Frankfort on the Main- Heddernheim, Germany, a corporation of Germany No Drawing. Application December 15, 1937, Serial No. 180,029. In Germany December 16,

' 1 Claim.

In the white metal bearings heretofore commonly used the base metal consists principally of tin or of lead. The tin generally contains additions of antimony, bismuth, copper, etc., whereas the lead is alloyed principally with antimony and bismuth. The bearing metals having a tin I which when added to this base metal alloy, form bearing purposes.

base have up to now been considered the best of their kind. But in consequence of their high tin content which amounts up to 90%, they are very expensive so that for the sake of economy the expensive tin has been replaced by the cheaper lead. The lead content is very often used in the same proportion as the tin in the tin bearing metals. Even the additions are very often the same.

Since, according to views very often held, such metal alloys are best suited for bearing purposes in which the structure is composed of various hard components, it should be theoretically possible to use every metal as base metal for a hearing metal alloy, provided that. other metals exist,

hard compounds with it. Aluminum is known to form numerous compounds with other metals and it has been proposed to use aluminum alloys for This has, on several occasions, been tried but with very little success considering the fact that most aluminum bearing metals of the type referred to contain hard comafter an extended time of working. 'Such additions are antimony and lead which may be present in quantities up to 10% each. The antimony forms with aluminum the compound AlSb which is present in the base alloy as bearing component. Lead does not combine with aluminum. According to the opinion of several experts it is not soluble at all in the aluminum. If aluminum be melted together with lead, at the time of solidification a separation of the aluminum and lead takes place i. e. the lead is as insoluble in the aluminum as oil in water. By adding antimony to the aluminum this sharp separation of lead from the aluminum is obviated, so that with the presence of a suflicient quantity of antimony larger quanties of lead are distributed in the aluminum, re-

sulting in an alloy which shows a structure more structure as also the other qualities of the known especially suitable for bearing purposes. Apart from aluminum an AlSb compound is contained in it, while lead is either alloyed with this Al-Sb compound, or else is segregated in form of small drops which form an improvement of the sliding 5 surface, inasmuch as in the case of interruption of the oiling or a sudden stoppage of the running of the bearing no damage will be caused to the axle. All tests made in this direction proved in every instance that the sliding surface of the axle was covered with a thin layer of the aluminum alloy, that could easily be removed.' The aluminum-antimony-lead-alloys have a crystalline white bearing metal. Thus they are easily formable even in a cold state.

The sliding properties have been ascertained with an especially suitable alloy consisting of 2.5% Pb, 2.5% Sb and the balance aluminum by a bearing testing installation. On that occasion specific surface pressures of about 200 kg./cm. could be reached at a speed of 10 m./sec., whereby the bearing temperature rose up to 100 C. The test axle that consisted, of non-hardened steel was perfectly smooth and free from indents at the end of the test. Apart from the bearing testing machine, tests were made in combustion motors in which the connecting rod bearings consisted of the new aluminum alloys. These combustion motors have been driven by an electrical motor, so that the hearings were fully charged. Also in that case the bearings of the new alloy proved successful, for during a working period of about 6 weeks the motor did not show any defects.

on further investigation of these alloys it was 85 shown that the lead and the antimony can be replaced in part at least by one of the metals of the group tin, cadmium, calcium and arsenic in quantitles of 0.1-5%. Thus it is possible to make use with equal success of an alloy of the following composition Per cent P 2.5 Sn p 1 8b---- 1. 5 Al Balance In cases in which the price of the bearing metal is of lesser importance, the tin content may also 55 be higher. An alloy having a higher tin content is about the following:

Per cent Pb 2. Sb 2. 3 Sn 5 Al Balance Since tin alloys well either with antimony or with lead, it is particularly valuable as addition to the ternary aluminum-lead-antimony-alloy, but also the other metals added to this three-part-alloy result in very useful bearing metals.

While the additional metals mentioned above influence chiefly the sliding properties, the further possible additions of at least one of the metals of the group consisting of copper, nickel, cobalt, iron, manganese and zinc in quantities of 0.1-% and silicon in quantities of 0.1'-3% especially effect a strengthening of the bearing metal which consequently is more suitable to resist higher pressures. Especially an addition of manganese has proved very eifective, inasmuch as it not only increases the hardness of the alloy, but even improves essentially the sliding properties. An alloy that proved particularly useful for the automobile motor is composed as follows:

Zn.-- 1 u.

Balance.

The addition of metals of a higher melting point further serves the purpose of making the bearing metals capable of resisting higher temperatures.

While it is correct that with most of the additional metals named above the melting point of aluminum is lowered to the eutectic point, thepresence of these metals having higher melting points, more especially if lead and tin with their lower melting point are present, result in the direction of a better resistance to higher temperatures. Bearing temperatures of up to 120 C. could be reached without a clinging or sticking to the axle having occurred. Naturally with such high temperatures the higher heat expansion of the aluminum alloys has to be taken into account by the provision of a greater bearingplay.

If the new bearing metals are used under favourable conditions, i. e., presence of ample quantities of lubricants, they show but a small wear, even after a comparatively short runningin period.

Summing up it may be said that with the new bearing metals having an aluminum base as compared with the hitherto known bearing metals, the following advantages exist:

1. Easier running-in.

2. High resistance to wear.

3. Possibility to use unhardened axles.

4. High resistance to temperature.

The alloys may be used in accordance with the invention for any casting method, as sand casting, chill casting, pressure die casting and centrifugal casting. -With centrifugal casting the temperatures and numbers of revolutions must be adjusted in such a way that the segregations remain at a minimum. The alloys may further be pressed, forged or rolled. In this respect it is surprising that the annealing in the drawing of rods and tubes may be accomplished at about 500 C. in spite of the lead and antimony content without a segregation of the alloys occurring thereby.

For the production of an alloy as uniform as possible, first of all antimony is melted together with aluminum whereupon lead is added as such or as a preliminary alloy.

The rolling possibility moreover makes it possible to roll up the alloys to a firmer sheet base that may consist of iron or copper alloys or also of hardenable aluminum alloys and to produce from the compound metal sheets thus obtained especially firm bearing shells.

Having thus set forth the nature of my invention what I claim is:

A bearing metal alloy containing about 1-10% of lead, 1-10% of antimony and 0.13% of silicon, the balance being substantially all aluminum.

EUGEN VADERS. 

